Creating a MongoClient without authentication, and executing client.server_info() results in

 OperationFailure: there are no users authenticated

Strangely, executing buildinfo: 1 in the mongo shell works without authentication.

The difference between the two calls at the server side:

PyMongo call:

 {{2018-04-19T11:09:05.663+0000 D COMMAND [conn42] assertion while executing command 'buildinfo' on database 'admin' with arguments '{ buildinfo: 1, lsid:

{ id: UUID("4da14329-8129-4396-a9d4-0bd437edc491") }

, $clusterTime: { clusterTime: Timestamp(1524136141, 1), signature:

{ keyId: 6546081529825591297, hash: BinData(0, 080455570CE489C46F29666BD3F30579B805AFD3) }

}, $readPreference: { mode: "secondaryPreferred" }, $db: "admin" }' and operationTime '{ ts: Timestamp(1524136141, 1) }': Unauthorized: there are no users authenticated}}{{}}

From Mongo Shell: the same, but no readPreference tag there.

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This worked in previous PyMongo/MongoDB versions.

There are Ansible bugs logged because of this:

https://github.com/ansible/ansible/issues/38998

https://github.com/ansible/ansible/issues/34153

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